In drilling operations it is frequently necessary to obtain a sample of drilled material to accurately monitor the material composition. In one type of system a stacked series of drop boxes are employed so that a sufficient amount of material can be collected to enable an adequate flow distribution of the material to be directed to a sampling apparatus. A sample extracted from the sampling apparatus can then give an indication of proportional quantities of minerals within the drilled material.
The existing type of double box system is affected by problems which can result in an inadequate flow distribution of material to the sampler. Such problems may be attributable to faulty operation of trap doors which are controlled to open and close the drop boxes to allow either build up or release of material therein.
One type of trap door design for a drop box consists of a V-shaped trough with rectangular openings which are opened or closed by trap doors which are hinged at their upper ends. Sometimes with this type of arrangement material can build up around the openings and block operation of the trap doors so that they are unable to close properly.